Fom fr.Wikipédia, I find "the posterity of Rudalt remains hypothetical.... On the basis of onomastics, Noël-Yves Tonnerre considers that it is likely that Rudalt is the FATHER or GRANDFATHER of Orscand de Vannes, bishops of Vannes, who died around 992, whose son is also named Rudalt; the ancestor of the Rieux lineage where we still record the regular alternation of the names Alain and Rudalt in the 11th century". — Citing André Chédeville & Hubert Guillotel, La Bretagne des saints et des rois : ve – xe siècle, Rennes, Ouest-France Université, 1984, 423 p. (ISBN 2858826137), p. 373.
https://fr.wikipedia.org/wiki/Rudalt_de_Vannes
It seems there's No firm support that Rudalt or Rodald had a son named Orscand I de Vannes . Medlands doesn't show Rudalt as a father. Moreover, Medlands cautiously brackets the entire bio for "Rodald" with Alain the Great being his father.
"a) [RODALD (-after 30 Nov 909). The Chronicle of Nantes quotes a charter, dated to after 5 Feb 897, under which "Alanus rex, summus Britonnum dux…conjugis nostræ Ohurguen ac…communis prolis" donated property, signed by "Rodaldi, Guerech, Pascultani, Budici"[75]. The charter does not specify the relationship between the donor and the four witnesses. However, other documents quoted below show that Guerec and Pascwethen were Alain´s sons. It therefore appears likely that Rodald and Budic were also his children. If this is correct, Rodald was presumably the oldest child as he is named first. The dating clause of a charter dated 30 Nov 909 refers to "Rudalt comite post mortem patri sui", referring to the county of Vannes[76]. Comte de Vannes. It appears that, after the death of Alain, power in Brittany was shared between the counts of Poher (Alain´s son-in-law), Vannes (Alain´s possible eldest son) and Cornouaïlle and that none of these was acknowledged as overall ruler.]"
http://fmg.ac/Projects/MedLands/BRITTANY.htm#_ftnref75
